The long-range goal of this project is to investigate the effects of halothane on liver cell structure in rats that have been subjected to one of two pre-treatments: (1) to hypoxia during anesthesia or (2) to prior treatment with Aroclor 1254, a polychlorinated biphenyl mixture known to induce an altered form of cytochrome P450 (cytochrome P449), a microsomal enzyme responsible for the metabolism of halothane. The project will systematically evaluate the effect of each of the pre-treatments alone or of nalothane alone on: (1) liver ultrastructure by electron microscopy, (2) the concentration of cytochrome P450(449) (as an index of the effective induction of the altered cytochrome) and (3) plasma fluoride concentration (as an index of the shift of halothane metabolism to a reductive pathway). The second phase of the project will evaluate the same parameters in animals subjected to the pre-treatments plus halothane. This study will help document the suitability of these preparations as models for the study of halothane-induced hepatitis, as suggested by other investigators. The morphologic changes will be assessed using morphometric techniques and will provide quantitative data for each of the treatments. The methods developed in this study should lead to a subsequent investigation of other anesthetics using similar technics. In particular, the application of morphometric analysis of electron microscopic images will provide a data base against which other anesthetics (e.g. halogenated ethers) may be compared.